Apparatus for heating fluids



Feb. l0, 1931. H. B. CANNON APPARATUS FOR HEATING FLUIDS Filed Jan. 5l, 1927 6 Sheets-Sheet l @fk/,MW

Feb. 10, 1931. H. B. CANNON APPARATUS FOR HEATING FLUIDS Filed Jan. 51, 1927 6 Sheets-Sheet 2 Snowdon Smm, 5

H. B. CANNON APPARATUS FOR HEATING FLUIDS Feb. 10, 19314o Filed Jan. 3l, 1927 6 Sheets-Sheet 5 Feb. 10, 1931. H. E. CANNON APPARATUS FORHEATING FLUIDs Filed Jan. 3l. 1927 6 Sheets-Sheet 4 Feb. 10, 1931,- H. B. CANNON AP'PARATUS FOR HEATING FLUIDS Filed Jan. 5l, 1927 6 Sheets-S1166?l 5 Patented Feb. 1o, 1931 PATENT ort-1era HIRAM B.V CANNON, OF ERIE, PENNSYLVANIA AIPPARATUS FOR HEATING FLUIDS Application led January 31, 1927. Serial No. 164,668.

rlhis invention relates to an apparatus for heating fluids, the embodiment of the apparatus shown anddescribed herein being a steamboiler installation. It is the general purpose and 'object of the invention to provide an apparatus of the character referred to which will utilize a high percentage of the heat units liberated by the combustion of thefuel; which will secure a high rate of combustion of the fuel; and which will secure' perfect combustion of the fuel, without injury to the furnace walls and the tubes or other fluid container. A further object of the invention is to providean apparatus which will enable a very considerable proportion of the boiler surface to be heated `by radiation from the -outer wall of a combustion chamber surrounded by such boiler surface and wherein a considerable proportion of the radiant heat from the combustion within suchwall will be. transferred to the said surface. A still further object of the invention is to provide a novel and cooperating construction of boiler and boiler furnace whereby maximumeiiiciency is obtained.

-Still further, and more limited objects of the invention will Aappear hereinafter and will be realized in and through the various features of construction illustrated in the ments and steps embodied in the claims.

The apparatus Vshown herein will be referred to generally7 as a boiler, which term will include both the steam generator and the cooperating furnace construction.

Referring to the drawings, Figs. 1 and 1 represent a central vertical sectional View through a steam-boiler constructed in accordance with my invention, certain parts being shown in elevation; Figs. 2, 3 and 4 are details in transverse section corresponding respectively to the lines 2 2, 3-3 and 4--4 of Fig..1 5 is a detail in vertical section of the lower portion of the boiler, showing a modification of the means for` supplying water to the lowerends of the vertical series of boiler tubes; Fig. 6 is an enlarged sectional detail corresponding to part of the line 6--6 of Fig. 3; Fig. 7 a sectional detailcorresponding to 59 th'e1ine7--7ofFig.'6;Fig. 8 a detail in section vdrawings and by the combinations of elecorresponding to the line 8-8 of Fig. 7 Fig. 9 a side elevation of one of the blocks for supporting the combustion chamber from the boiler tubes; Fig. 9a a plan view of one of saidblocks; Fig. .10a side elevation of one of the blocks or bricks of which the wall of. the combustion chamber is composed; Fig.. 11 a view, similar to Fig. 8, showing a modification.; and Figs. 12 and 13 are cross-sectional views' showing modified forms of my 60 combustion chamber.

Describing the various parts by reference characters, 1 denotes upright members, shown as I-beams and which support at their upper ends transverse members 2 also shown as I- 65 beams. The members 1 and 2 are so arranged that the members 2 form a'rectangular horizontal support for the bottom of the boiler casing of the furnace and the parts thereabove, it being noted, by reference to Fig. 3, that the ends of one pair of such members 2 extend beyond the said casing and the parts thereabove 'while the ends of the other pair preferably do not extend beyond the casing. 3 denotes the base of the boiler casing and the 7 5 hearth or bottom for the combustion chamber. This base is made of suitable refractory material having high heat-and-slag resistance and low heat-conductivity. Magnesite or like material is suitable for this purpose. The base is provided with 'a shoulder 3a on its undersurface by means of which it is supported on the beams 2 and is provided with an extension 4, within such beams, providing an ash pit, said pit being encased with heat-insulating material4a and a metal shell 4*. Extending upwardly from the outer edge ofthe base 3 is a boiler casing 5, which casing is pref-l erably made of material having low heat conductivity and high heat-reflecting properties, silocel or Infrax being examples of such material. On top of the casing is a stack 6.

7 denotes a combustion chamber which is located within and spaced from the lower part of the casing, with its lower end supported on the base 3. The outer wall orwalls of this combustion chamber should be composed,

`in part at least, of refractory-material having high heat-radiating capacity at high temperatures, the best material for this purpose be- 10 of the combustion chamber being preferably geveled outwardly and upwardly as shown at The casing 5 and the combustion chamber 7 are preferably square in section, providing spaces between the sides thereof for the tubes of the boiler proper, which will now be described. 10 denotes a water-and-steam drum which is supported outside of and near the `top of the casing 5. From the bottom of this drum, pipes 11, 12, 13 and 14 connect the bottom of the said drum with headers 15, 16, 17 and 18, respectively (see Fig. 4) the said headers being located below the shoulder 3 and each being located below one of the four spaces A provided between the side walls of the coinbustion chamber and the inner walls of the casing. From each of the headers 15, 16, 17 and 18, a series of vertical tubes 15, 16a, 17 and 18, respectively, extends upwardly through the spaces A thereabove, in proximi- I ty to but yout of contact with the outer walls of the combustion chamber adjacent thereto, and through the shoulder 9 and in proximity to the inner sides of the casing 5. The tubes '15a of one series are connected at their upper ends to the drum 10; while the tubes in the other series are connected at their upper ends to headers or drums 16, 17 b and 18, respectively. The drums or headers 16b and 18b are connected to the drum 10 by short connections 16c and 18c respectively, while the drum or header 17 F is connected to the drum 10 by means of an uper and a lower series oftubes 19, 19a which extend upwardly from said drum or header across the casing 5.

20 denotes a header which is connected with the top of the drum 10 by a connection 21 and from which header vertical coils 22 of a superheater extend through and across the casing y u latter to be raised quickly to and maintained 5, 4above the tubes 19, 19,.the lower ends of the superheater tubes being connected with a header 23 'from which a delivery pipe 24 extends.

In the stack 6, above the superheater coil, is an air heater, indicated generally at 25, the said heater being provided with a supply duct 26 and a delivery duct 27 extending downwardly to a bustle pi e 28 whichl extends about the casing 5, above t e lower end thereof. From this pipe there depend four supply pipes 29 from each of which in turn a short,

pipe 30 projects inwardly toward a corner of the casing 5. The pipes 30 are for the purpose of supplying secondary preheated air for the combustion of the mixture of fuel and primary air supplied to the burners, indicated generally at B. Each burner is supplied with such mixture of fuel and primary air through vertical pipes 31 extending into the T 32 which supports the burner proper. With the embodiment of my invention as shown herein, it is contemplated that the burners shall be supplied with pulverized fuel, and the pipes 31 are for the purpose of conducting air, or like combustible fluid under pressure, together with the powdered fuel suspended therein, to the respective burners, this mixture of fuel and air being further mixed with the hot air delivered through the pipes 29 and 30.

It will be noted, from Figs. l and 3, that the burners are generally triangular or fan shaped, each being provided with an elongated dischar e slot B', the said slots being arranged vertically and the burners projecting through the corner portions of the casing 5 and of the combustion chamber 7 but with their axes slightly out of coincidence with diagonals connecting such corners. This arrangement is shown in Fig. 3, wherein it will be seen that the inner wall B2 of the mixture discharged by each burner into the combustion chamber is approximately in a vertical plane connecting the diagonally opposite cornersof the combustion chamber, while the outer wall B3 of such mixture diverges from such plane. The result of this arrangement is that thev fuel mixtures delivered by the four burners will impinge close to the center of the combustion chamber, producinr a vortex action about the vertical axis ofa the said chamber. The purpose of this arrangement of the burners or nozzles is to enable a quick and complete admixture of the air and powdered fuel and a quick and complete combustion of such mixture to be obtained entirely within the combustion chamber when the wall or walls thereof are at a high temperature. This `quick and complete combustion not only enables 'me to burn a very large quantity of fuel in proportion to the size of the combustion chamber, but to burn the same completely and without injury to the wall of the combustion chamber, while enabling the Athe manner of Vburning' the fuel therein, this fuel is completely consumed by the time it has reached the top of saidV chamber.

In actual operation, the combustible streams, from the moment when they leave IBO the burners until they reach the center of the vortex, are indicated by dazzling white, horizontally expanding, vertical bands of flame. There is little other evidence of flame Within the zone extending from the bottom to the top of the burner openings, as above described. Furthermore, the, combustion reaction above the top plane of theburners is practically transparent. This transparent condition ofthecoinbustion zone'enables me to obtain a maximum transfer of radiant heat therefrom through the walls of the combustion chamber to the tubes V15a-18'EL adjacent thereto, and directly to' exposed portions of.

maintained, radiant heat reflected from and re-ra'diated by the inner surfaces of the Walls assists in securing early ignition of the combustible mixture delivered by the burner nozzles and an early reduction of the solid carbon constituents of such mixture to gase- `ous combinations thereof, which gaseous combinations `are completely reduced by the hot zone provided by the said chamber, even though the chamber is comparatively short.

The tubes 15a-18a, being spaced from the walls of the casing 5, are not cooled on their outer sides by'such walls and, being spaced from the walls 7, their inner sides do not tend to cool such Walls and increase the resistance of the latter to the'transfer of radiant heat tothe said tubes, as would be the case were the disposition of the walls and tubes some-` what-intimate or merged. The casing 5, lbeing made ofheat-reflecting, as well as heatinsulating, material, assists materially in the heating of the tubes yby reflecting against the outer surfaces thereof the heat received by 'radiation from the combustion chamber 7.

'Ihe4 steam generated in the tubes 15a-18a-is delivered to the drum 10, it being noted that therebetween. As the products of combustion vcontinue to rise, they pass 1n contactk with the superheater coils 22 and thence tol the air .heater 25.' l

Reference has been vmade hereinbefore-'to the ability of the'fu'rnace part of my Ainvention to secure a very high rate of combustion without injury to the radiating screen formed by the Wall or walls 7 of the combustion chamber and to secure the transfer of a considerable proportion of the heat'units developed by such combustion to the tubes 15a-48a by radiation from said screen, and to accomplish this result Without elevating the temperatures ofthe' wall or Walls 7 to a destructive point. The heightI and cross sectional area of the combustion chamber are so designed with reference to the type of burners employed and the rate of combustion ofthe mixture delivered thereby as to secure these results. For instance, I have found that I can operate my boiler and furnace unit .at a combustion speed ranging from 180,000 to 37 5,000 B. t. u.s released per cubic ffootof combustion space per hour, these figures being based on the space enclosed by the combustion chamber. At the same time, the B. t. u. absorption per square-foot of boiler absorbing surface may be as much as 100,000 or more per hour, especially in the tubes 19, 19'a and those surfaces of the tubes 15-18a which aregexposed directly to the combustion volume, such absorption being dependent upon ,the means used to provide positive circulation of the boiler fluid. lProvided that the upper limit of combustion speed is not exceeded, the wall or walls 7 -will not be dei stroyed through siagging action. The radiating screen constituted by the wall or walls 7 is used primarily to maintain thecombustion zone at a very high temperature, so that the combustible matter discharged thereinto by the burners may be very quickly and completely consumed. The screen also protects the boiler tubes adjacent this combustion zone fromdestruction by direct conta-ct with the flames within the said screen. The general arrangement of the burner nozzles is also important in securing the kind of combustion within the Wall or walls 7 that will enable the high rate of combustion and the high percentage of heat transfer to the tubes to be effected. By directing the streams from the burners as closely to the axis C as indicated, I am enabled to limit the luminous or opaque condition ofthe combustion reaction to a zone which does not extend materially ab'ove the plane of the tops of the burner; and this arrangement not only enables me to burn completely a large quantity of fuel, as pointed out hereinbefore, but enables me to do so without subjecting the-walls of the combustion chamber to destructive slag and '-vented by circulating products of combustion through the vertical spaces A between the' said lwalls and the casing 5. To accom-- plish` this purpose a pipe 33 is connected with the stack above the air heater, with its lower l end connected with a blower 34 which deliversI the said products to a bustle pipe 35 surrounding the casing 5 and the lower end of the combustion chamber and delivering such products into the bottoms of the spaces A through connections or tuyres 36. The flanges or shoulders 9 are'provided with slots 9a permitting the circulation of the products through the spaces A.

When operating at an excessive rating, it is desirable to employ positive means for forcing the liquid from the drum 10 into the bottoms of the tubes a-18a. 'An arrangement for accomplishing this purpose is shown in Fig. 5, wherein one of the down pipes from the drum 10 is shown as provided at the y lower inwardly-deflected end thereof with a pump, which may be of the turbine type and which is indicated conventionally at 37, the pump shaft 38 being driven by a motor 39. In this view only one of the pipes is shown, the pipe being designated 11a and communieating at its lower end with a drum or header 15. This arrangement insures a positive and forced circulation of the liquid from the drum 10 to the various lower headers and upwardly into and through the tubes 15a- 19a thereabove, which circulation will prevent blistering of the'said tubes, the arrangement insuring the presence, of the liquid, as such, in the tubes 15u-18a.

In Fig. 12 there is shown a. modification of my invention wherein only two opposed walls 7 of the combustion. chamber are of silicon carbide.' The other two walls are composite walls, each consisting of an inner facing 7a of refractory material and a metal backing 7", to which the tubes 16a and 18a are clamped, as shown at 7 c. The composite walls are preferably made up of blocks.

In Fig. 13 there is shown a further modification of the invention wherein two opposed f Walls 7 are of silicon carbide, the other two n opposed walls being formed by the tubes 16a and 18a, which tubes are provided with fins 16b and 18", respectively, the fins on the casing tubes meeting and enabling the tubes and quate amount of heatv in the furnace for burn! fins on each side to constitute a wall, as before stated. In both Figs. 12 and 13, the outer surfaces of the tubes 16a and 18a are shown asin substantial contact with the inner wall of the outer casing.

In all forms of my invention, at least two opposite walls of the combustion chamber are formed of a. material having high heatradiating capacity at high temperatures and serving to heat by radiation tubes outside and spaced therefrom. This enables sufficient sensible heat to ybe stored to maintain an adeing the fuel. p

The combustion chamber, as pointed out hereinbefore, will function with maximum 'efficiency where the wall or walls thereof are made principally of silicon carbide. l In practice, where such material is used, the walls of the chamber are built up from a plurality of blocks 8 united by inter-engaging tongues and grooves. In the drawing (see Figs. 6 and 10) each such block is shown as provided with a tongue'Sa on the upper face thereof and a corresponding groove 8b on the lower face thereof, the said tongues and grooves extending in the direction of the length of thewall of which the blocks form a part. In addition, each block 8'is provided with a tongue 8'3 at one end thereof and a groove 8d at the other end thereof. The tongues 8c and grooves 8dl extend vertically in'the wall of which they form a part. To stabilize the walls of the combustion chamber, they are tied or anchored to pairs 'of tubes in the series 15u-18, as shown in Figs. 3 and 6-11 inclusive, each side wall of the combustion chamber being provided with outwardly extending anchoring header walls, indicated generally at D, which will be described in detail.

Each wall D consists of a vertical series of header blocks 40, each of the said blocks being preferably silicon carbide and being conveniently of twice the height of the blocks or tiles 8. Each block 40 is provided with a pair of tongues 40a, 40h. extending across' the top thereof and a pair of grooves 40, 40d extending across the bottom thereof. In addition, a vertical groove 41 inl one face of the block connects thel ends of the tongue 40b and grove 40d adjacent such face; and a tongue 41 on the opposite face of said block connects the ends of the tongue 40b and groove 40d adjacent to such face. affords an effective means for interlocking the header blocks 40 with the blocks 8 and with the Walls 7 composedof such blocks. By inserting the right-hand end of each block 40 between the opposed ends of two pairs of blocks 8 the blocks 40 will be interloclred with the bloclis 8 by the engagement of the tongues 8c with the grooves 41 and by the engagement of the tongue 41a with the grooves 8d; while the blocks 40 will be interlocked with each other by means of the tongues 40, 40b and the grooves 40e, 40d.

In order to secure the header walls D, formed by the block s 40, to the pipes, I have provided two forms of connection, thyit shown in Figs. 6-8, and that shown in Fig. 11. In Figs. 6-8, each pipe to which a wall D is to be connected isprovided with vertically spaced lugs 15d, the lugs-being preferably welded to the pipes, each lug having a vertical slot 15 therethrough, lwhich slot receives the reduced threadedvend of a stud 42, the stud being secured to the lug by means of a nut 43 on such threaded end. The opposite end ofeach stud is adapted @o enter a diagonal shallow slot 44 providd therefor in one of the blocks 40. This arrangement enables the studs to be assembled readily with reference .to the lu s 15d and the header blocks should the sait? blocks be somewhat out of alignment and at the same time enables the studs to be adjusted to inal position with their upper faces engaging the upper inclined surfaces of vthe slots 44, whereby they will sustainthe outer or projecting ends of the blocks.. It will be noted that Athe lugs 151 and the studs 42 are staggered on the pipes comprising each pair, one pipe 15L being connected to`hal of the blocks while the other pipe is connected to the other halt of the blocks 40 in the common Wall D.

In Fig. 11 there is shown a modification wherein each of the blocks 40 is supported from a pipe (such as 15a) by means of studsV each of which is carried by a clamp 46 which extends about a portion o the pipe by which the stud is supported, `each stud 'being provided with a screw 47 threaded therethrough and adapted to engage the adjacent surface of the tube. The end of each clamp 46 is spaced less than 180 degrees from the end of the screw 47 so that, when the screwsare set up, the clamps will be forced against their respective pipes and will each aiord an adequate support for' the stud carried thereby. The combustion chamber is further stabilized by the shoulder 9 which engages the casing 5 and by the pipes 15)--18a extending through said shoul- The boiler installation described herein is particularly eiiicient for use with pulverized fuel and makes eective' use of the radiating effect of the incandescent ashupon the exposed portions of the tubes 1584-18, this effect being materially greater on these tubes than on the top bank of tubes 19, 19a. This enables me to cool the ash far below the temperature at which it becomes molten, by the time it reaches the tubes 19, 19, thereby preventing the glazing or the forming of a solid deposition of ash on vsuch tubes. vConsequently, the side wall tubes 15-18a as exposed serve theabove 'purpose as well as absorb re-radiation from the inner surface of the screen or wall 7 v and also direct radiations from combustion reactionsthroughout the combustion zone; and it is proper to state that these exposed tubes prevent the blistering or destruction of the top bank of tubes 19, 19B.

In operating with pulverized fuel, they matter of removing the` slag is important. The arrangement of the burnersB produces (as stated hereinbefore) an opaque ila'me above the hearth or base 3, and this flame protects the hearth or base against concentrated heat radiation from within thefiame as well as from the transparent combustion zone thereabove, and thus avoids heating the hearth or base to the critical temperature at which the molten slag would react with the hearth or base to destroy'the latteral This molten slag will flow down the inclined top of the base and will be delivered through the central'opening therein into a car 48 in the pit therebelow, the car, when lfilled, being removed .through a-suitable door 49.

Having thus described my invention, what I claimv is:

1. Ina boiler, the combination of a vertically extending casin composed of heatresistant and heat-re ecting material, a combustion chamber located in the lower portion of the said casing and spaced therefrom and arranged to discharge into the portion of the said casing thereabove, the` said combustion chamber being composed vprincipally of material having high heatradiatin qualities at high temperatures, headers beneath the space provided between the casing and the com ustion chamber, a steam and water drum arranged above and beyond the top of the combustion chamber, downcomer tubes connecting the said drum with each of said headers, a vertical series of tubes extending, upwardly from each header through the space between thev casing and the combustion chamber and along the inner wall of the casing above and beyond such chamber and'having their upper ends connected to said drum, one such series of tubes extending across the casing above the combustionv chamber, and means ffor deliverin a fuel mixture to the lower portion o said combustion chamber4 and for Earning the mixture within the said `charla- 2. In a boiler, the combination of a vertically extending casing polygonal in section andA composed of heat-resistant and heatreflecting material, a combustion chamber also polygonal in cross section and located in the lower portion of the said casing and spaced therefrom and arranged to discharge into the portion of the said casing there.-

above, thel said combustion chamber being composed principally of4 material having high heat-radiating .qualities at Ahigh temperatures, a header beneath the space pro.- vided between each wall of the casing and each wall of the combustion chamber, a steam and water drum 'arranged above and beyond the to downcomer tu esconnecting the said druxmy with each of said headers, a vertical series. of.

ers' and said drum, one of said connectionsA of the combustion chamber,v

comprising tubes extending across said casing, and means for deliverlng a mixture of pulverized fuel and a combustion-supportlng agent to the lower portion of said combustion chamber for burning the mixture within said chamber. i

3. The combination, with a combustion chamber wall, of spaced fluid-conducting tubes arranged adjacent to the said combustion chamber, header blocks keyed into and projecting outwardly from the said combustion chamber between pairs of said tubes, and means adjustably connecting the header blocks to the tubes of each pair thereby to stabilize the said combustion chamber, the said means comprising studs adjustably secured-to said tubes and each having an end enterin an inclined slot in the face ofthe header lock adjacent thereto.

4. A combustion chamber wall for a .fluid heater embodying spaced tubes adapted to extend in proximity to said Wall, the said wallcomprising a plurality of interlocking blocks, header blocks interposed between blocks of said wall and interlocked therewith and with each other, and means ,securing said header blocks to said tubes thereby to stabilize the said wall.

5. In a boiler, the combination of a vertical combustion chamber composed principally of refractory material having high heat-radiating capacity athigh temperatures, a vertical v casin surrounding the said combustion cham er and spaced therefrom and extendingetherebeyond, vertically extending boiler tu s in the space between said chamber and casing and each having a portion thereof extending above and beyond said chamber and into the path of the products of combustion s discharged from said chamber, and means for supplying a combustible mixture to said combustion chamber and for completing the combustion of said mixture within the said chamber whereby the flame of combustion is kept out of contact with'the tubes in the zone ,of most intense combustion and the said tubes are heated by radiation from said combustion chamber in such zone as well as by the sensible heat of the products ofcombustion in the zone'beyond the combustion chamber.

- 6. In a boiler, the combination of a vertical combustion chamber composed principally of refractory material having high heat-radiating capacity at high temperatures, a vertical casin surrounding the said combustion cham er and spaced therefrom and extending therebeyond, vertically extending boiler tubes Y and eac in the s having a portion thereof extending above and beyond said chamber: and into the path ofv the 'products of combustion dis-,- charged from said chamber,

plying a combustible mixture to said com# *e bustion chamber and forcompleting the com- Y bustion of said mixture within the ,said chamace between said chamberandcasing means for sup-J ber whereby the flame of combustion is kept out of contact with the tubes Vin the zone of most intense combustion and the said tubes are heated by radiation from said combustion yond the upper ends of said tubes and for circulating the same through the space between the casing and' the combustion chamber thereby to prevent oxidation of said chamber.

7. In a boiler, the combination of a vertical combustion chamber composed principally of refractory material having high heat-radiating capacityat high temperatures, a vertical casin surrounding the said combustion cham er and s aced therefrom and extending therebeyon vertically extending tubes in the space between said chamber and casing and each having a ortion thereof extending above and beyond t e said chamber and into the path-of the products of combustion discharged from said chamber, means for supplying a combustible mixture to lsaid combustion chamber and for completing the combustion of said mixture within the said chamber whereby the flame of combustion is kept out of contact with the tubes in the zone of most intense combustionand the said tubes are heated by radiation from-said 'combustion chamber'in such zone as well as by the sensible heat of they products of combustion in vthe zone beyond the combustion chamber,

and spaced means for supporting the combustion chamber from the said tubes.

8. In a boiler, the combination of a vertical combustion chamber composed principally of refractory material having high heat-radiating capacity at high temperatures, a vertical casing surrounding the said combustion chamber and spaced therefrom and extending therebeyond, verticall extending tubes in the space between said c amber and casing and each havinga ortion thereof extending above and beyond t e said chamber and into the path of the products of combustion discharged from said chamber, means for supplying a combustible mixture to said combustion chamber and for completingthe combustion of said mixture with-in the said charnber whereby the flame of combustion is kept out of contact with the tubes in the zone of most intense combustion and the said tubes f are heated by radiation from said combustion chamber in such zone aswell as by the sensible heat of the products of combustion in the zone beyond the combustion chamber, spaced means for supporting thel combustion chamber from the said tubes, and, means for positively circulating liquid upwardly through the said tubes. I l

9. In a boiler, the combination of a vertical leasing, a combustion chamber within the the said combustion radiating lower end of the and spaced therefrom, amber beingzomposed principally of ,material having gh heatboiler tu es extending upwardly through the space between the combustion chamber and the casing and along the inner wall` ofthe casing beyond the said combustion chamber, means for s'uppl ing a mixture of pulverized fuel and a 'combustion-'sup rting agent to4 Y the combustion vchamber an for substantialwithin .Y the lower portion only ofthe casing and having high spaced therefrom, the said combustion chamber being composed principally of material heat-radiating capacity at high temperatures, boiler tubes extending upwardl throughthe space between the combustion c amber and the casing and along the :inner vwall of the casing beyond the said combustion chamber, means' for supplying a mixture of pulverized fuel and a combustion-supporting agent to the combustion chamber land for substantially completing the combustion of the mixture within the said chamber, .additional boiler tubes extendingl transversely of the casinghalive the upper end of the comber ands bustion c aced therefrom a sullicient distance to enab e the ash reduced by the combustion-of the fuel to cooled below coalescence by the exposed portions of the first mentioned tubes before the ash reaches the second group of tubes, and means for positivel circulating li uid verticallythrough the mentioned tubes.

11. In a boiler, the combination of a vertical casing, a combustion chamber in the" lower portion of "said casing and spaced therefrom, the said combustion chamber being composed principally of refractory material having high heat-radiating capacity at high temperatures, an elevatedv steam and water drum located above and beyond the upper end of the combustion chamber, boiler 'tubes extending upwardly through the space between the said combustion `c amber and into the casing above and beyond the said v combustion chamber and communicating at capacity at high temperatures,

toms of said tubes, and means for producinga forced circulation of such liquid upwardly through the said tubes and into said drum.

12. In a boiler, the combination of a vertical casing, a combustion chamber within `and at one end of the casing and spaced therefrom, the rsaid combustion chamber being composed yprincipally of material having 'high heat-radiating capacity at high temperatures, boiler tubes extending upwardly through the space between the combustion chamber and the'casing and along the inner wall of the casing above and beyond the said combustion chamber, additional boiler tubes extending transversely of the casin above and beyond the upper end of the com ustion chamber, means for supplying a mixture of from, the said combustion chamber being composed principally of material having high heat-radiating atures, boiler tu es extending upwardly through the space between the combustion chamber and into the casing beyond the said chamber, additional boiler tubes extending transversely of the casing adjacent to the upper ends of the former tubes, means for supplying a mixture ofpulverized fuel and a combustion supporting agent to the combustion chamber and for substantially completing the combustion ofthe mixture within the said chamber means for producing a forced circulation of tubes, means for with awing a limited proportion of the products of combustion from a znebeyond the upper ends of said-tubes and for circulating the same through the space between the casing and the combustion porting the chamberfrom the firstmen- -tioned tubes.

capacity at high temper-t liquid u wardly through said In testimony whereof, I hereunto aix my signature. HIBAMB. CANNON.

their upper ends with said drum, means for supplying a combustible mixture to the said Y combustion chamber and for substantially y coinpleting the combustion of the said mii:-` ture in the said chamber, connections for supplying liquid from the said drum to the bot'- 

